There is a call from a group of health advocates to yank a Facebook app off the market. They claim the messenger app for kids is a threat to their well-being.

There are 97 child advocates who signed the letter, including individuals and non-profits. They're asking Facebook to pull the plug on Messenger Kids.

It is an advertising free Facebook app targeted at 6 to 12-years-olds. Facebook says it took steps to be responsible with the app, including giving parents tools to control their children's social media use. But those against the app sent Mark Zuckerberg a letter -- pointing to recent studies that show social media can be damaging to young people.

Here's a quote from the letter: "Younger children are simply not ready to have social media accounts. They are not old enough to navigate the complexities of online relationships, which often lead to misunderstandings and conflicts even among more mature users."

They go on to point to studies that show social media use by teens is tied to higher rates of depression.

There is no reaction yet from Facebook CEO Mark Zuckerberg, who is a father of two.